An example of a conventional electrostatic precipitator (ESP), module or system 100 is depicted in simplified form in FIG. 1A. The exemplary ESP module 100 includes a corona discharge electrode 102 (also known as an emitter electrode) and a plurality of collector electrodes 104. A driver electrode 106 is located between each pair of collector electrodes. In the embodiment shown there are four collector electrodes 104a, 104b, 104c and 104d, and three driver electrodes 106a, 106b and 106c. The corona discharge electrode 102, which is likely a wire, is shown as receiving a negative charge. The collector electrodes 104, which are likely metal plates, are shown as receiving a positive charge. The driver electrodes 106, which are also likely metal plates, are shown as receiving a negative charge. FIG. 1B illustrates exemplary dimensions for the system or module of FIG. 1A.
The voltage difference between the discharge electrode 102 and the upstream portions or ends of the collector electrodes 104 create a corona discharge from the discharge electrode 102. This corona discharge ionizes (i.e., charges) the air in the vicinity of the discharge electrode 102 (i.e., within the ionization region 110). As air flows through the ionization region 110, in the direction indicated by an arrow 150, particulate matter in the airflow is charged (in this case, negatively charged). As the charged particulate matter moves toward the collector region 120, the particulate matter is electrostatically attracted to and collects on the surfaces of the collector electrodes 104, where it remains, thus conditioning the flow of air. Further, the corona discharge produced by the electrode 102 can release ozone into the ambient environment, which can eliminate odors that are entrained in the airflow, but is generally undesirable in excess quantities. The driver electrodes 106, which have a similar charge as the particles (negative, in this case) repel or push the particles toward the collector electrodes 104, thereby increasing precipitation efficiency (also known as collection efficiency). However, because the negatively charged driver electrodes 106 are located close to adjacent positively charged collector electrodes 104, undesirable arcing (also known as breakdown or sparking) will occur between the collector electrodes 104 and the driver electrodes 106 if the potential difference there-between is too high, or if a carbon path is produced between the a collecting electrode 104 and a driver electrode 106 (e.g., due to a moth or other insect that got stuck between an electrode 104 and electrode 106, or due to dust buildup). It is also noted that driver electrodes 106 are sometimes referred to as interstitial electrodes, because they are situated between other (i.e., collector) electrodes.
Increasing the voltage difference between the driver electrodes 106 and the collector electrodes 108 is one way to further increase particle collecting efficiency. However, the extent that the voltage difference can be increased is limited because arcing will eventually occur between the collector electrodes 104 and the driver electrodes 106. Such arcing will typically decrease the collecting efficiency of the system.
Accordingly, there is a desire to improve upon existing ESP techniques. More specifically, there is a desire to increase particle collecting efficiency and to reduce arcing between electrodes.